"How I Met Your Mother" continued its slow march to the Robin-Barney wedding with "The Rehearsal Dinner." This week's few minutes of time featured paintball, an ice rink full of Canadians -- including Alan Thicke -- and some bad Italian.But there's a chance that all of this was upstaged by one anonymous, rapidly aging couple seen only in the background.Paintball vs. an ode to CanadaWhen most couples plan a rehearsal dinner, they go with an intimate, beautiful meal in which close family and members of the wedding party can anticipate the big event. That's not the route that Barney and Robin took.Instead, Barney insists stubbornly that a paintball dinner would be best, because of course he wants a paintball dinner. Robin, meanwhile, wants some sort of Canadian affair. What that means remains something of a mystery, since all of the Canada talk quickly devolves into endless jokes about mittens and Tim Hortons.Still, it seems...